The present invention relates to an apparatus for tissue treatment, such as cosmetic tissue treatment.
It is known to utilise laser light for tissue treatment, such as cosmetic tissue treatment, removal of hair, photocoagulation of veins, etc.
During cosmetic tissue treatment, a laser ablates a thin epidermal layer of illuminated derma of a patient. During healing, a new epidermal layer is formed on the ablated surface having the look of the derma of a young person, i.e. the new epidermal layer is formed without previously existing scars, wrinkles, etc.
Lasers that operate at a wavelength that is absorbed in water are used for cosmetic tissue treatment. When the laser power density (W/mm2) at illuminated cells is sufficient, cellular water is superheated causing small explosions that disrupt heated cells.
During removal of an epidermal layer, it is essential not to damage underlying or surrounding tissue. Residual heat may cause non-ablated cells to char and become necrotic, whereby new scars may be formed and thus, it is desirable to apply laser power for a short time, to minimize transmission of conducted heat to underlying and surrounding tissue.
It is therefore desired to accurately control the amount of light energy transferred to derma to be ablated. The amount of energy must be sufficient for the dermal cells to vaporize and, simultaneously, the amount of residual energy heating non-ablated cells must be so low that non-ablated cells will not be damaged.
Apparatuses for cosmetic tissue treatment are known, comprising a CO2 laser emitting a laser beam and a laser articulating arm with mirrors for reflection of the laser beam, so that the laser beam is transmitted inside the articulating arm. Further, the arm has a number of joints, so that the arm can be moved around by an operator. A handpiece to be held by the operator is connected to the arm. The laser beam is moved or scanned across a target surface by adjustable mirrors connected to motors and mounted in the arm. The scan pattern of the laser beam is an archimedes spiral. The laser spot formed by the laser beam on the target surface moves along the spiral at a constant angular speed.
It is a disadvantage of the known apparatus that the energy density delivered to the target surface is non-uniform across the scanned surface area of the spiral, as more energy is delivered at the centre of the spiral than at the circumferential of the spiral.
It is another disadvantage of the known apparatus that the circular outline of the scan pattern leads to non-uniform scanning of an area that is larger than the area of the scan spiral as either 1) areas that have not been scanned will remain on the surface, when abutting spirals or 2) ablated areas will be scanned more than once, due to overlap of spirals.
It is yet another disadvantage of the known apparatus that evaporated derma is exhausted through the internal of the laser articulation arm, whereby optics and other members in the arm get dirty.
It is still another disadvantage of the known apparatus that it is very laborious to disassemble members, that may have been in contact with a patient, from the handpiece, e.g., for autoclaving.
It is still another disadvantage of the known apparatus that movement of the handpiece is restrained by the laser articulation arm, as the construction of tubes interconnected by joints is not fully flexible.
In addition, the apparatus typically has a large mass and a large inertia (typically also due to counter-balancing masses) which makes the operation and movement of the arm difficult and heavy.
Under the name Uni-laser 450P, Asah Medico A/S, Denmark, markets an apparatus for cosmetic tissue treatment, comprising a CO2 laser and an optical fiber coupled to the laser at one end and to a handpiece at the other end. The laser beam is manually scanned across the treatment surface by corresponding movement of the handpiece whereby the quality of the treatment is determined and limited by the skill of the operator.
Apart from being able to accurately control the amount of light energy transmitted towards tissue to be treated, it is also desirable to be able to automatically control whether or not light is transmitted towards tissue. If, for example, a laser is pointed at healthy tissue, it is desirable that it is detected that the tissue is healthy and that transmission of a laser beam be inhibited whereby damage to healthy tissue is prevented.
It is a disadvantage of known apparatuses that the exact circumference of the surface tissue area to be treated is defined manually by the operator. Manual control easily results in accidental damage to healthy tissue due to involuntary movements of the hand.
In U.S. Pat. No. 5,531,740, an apparatus is disclosed for automatically delivering a laser beam to an intricated colored region of a treatment area, e.g. for laser photocoagulation treatment of malformed veins. Typically, venular malformation forms an extremely intricate pattern and consequently, the task of precisely delivering the laser beam exclusively to the malformed veins becomes quite formidable. During scanning over the treatment region, the color of tissue to be treated is detected and the laser automatically treats only areas having a specified color.
It is a disadvantage of the apparatus that it is bulky and cannot easily be moved into treatment positions in relation to various surfaces of a human body. Rather, a tissue surface to be treated has to be brought into a specific position in relation to the apparatus before treatment can take place.
It is still another disadvantage of the known apparatuses that the distance between the surface to be treated and the output laser beam optics is unknown so that the degree of focusing of the laser beam on the surface to be treated is dependent on the operator.
It is yet another disadvantage of known apparatuses that no feed-back on the quality of the treatment currently in progress is provided.
It is an object of the present invention to provide an apparatus for tissue treatment having a handpiece that can be moved around, i.e. traversed and rotated, freely by an operator, i.e. without exerting forces acting against the movement.
It is another object of the present invention to provide an apparatus for tissue treatment in which one or more tissue parameters at the area to be illuminated by the treating light beam is detected and in which parameters of the laser beam is adjusted according to detected tissue parameter or parameters.
It is still another object of the invention to control parameters of the treating light beam according to the detected tissue parameter or tissue parameters whereby various types of tissue can automatically be treated differently.
It is a further object of the present invention to provide an apparatus for tissue treatment that include means for detecting the distance between the surface of tissue to be treated and the output optics focusing treating light onto the surface so that optimum focusing conditions may automatically be obtained during treatment.
It is still another object of the present invention to provide an apparatus for tissue treatment that includes a temperature measuring device for measurement of tissue surface temperature.
It is yet still another object of the present invention to provide an apparatus for tissue treatment that is adapted to automatically and accurately treat tissue to a desired depth causing only a minimum of damage to surrounding tissue that are not treated.
It is a further object of the present invention to provide an apparatus for cosmetic tissue treatment that is adapted to ablate dermal cells uniformly and from a large area of a patient.
According to a first aspect of the invention, the above-mentioned and other objects are fulfilled by an apparatus for tissue treatment, comprising a light emitter for emission of a first light beam and an optical fiber for transmission of the light beam. The fiber has a beam-inlet end that is aligned with the emitted light beam so that the first light beam is coupled into the optical fiber and a beam-outlet end for emission of the transmitted light beam. Further, the apparatus comprises a handpiece coupled to the optical fiber at the beam-outlet end and comprising an output for emission of the first light beam towards a target area of tissue to be treated, deflection means for adjustable deflection of the light beam, detector means for detecting at least one tissue parameter at the target area, and first light beam control means for controlling parameters of the first light beam deflected by the deflection means in response to the detected at least one tissue parameter whereby various types of tissue can automatically be treated differently.
According to a second aspect of the invention, an apparatus for tissue treatment is provided, comprising a light emitter for emission of a first light beam and means for directing the first light beam towards a target area to be treated. The apparatus further comprises detector means for detecting at least one tissue parameter at the target area, and first light beam control means for controlling parameters of the first light beam in response to the detected at least one tissue parameter without interruption of the propagating light beam.
According to a third aspect of the invention, an apparatus for tissue treatment is provided wherein at least one tissue parameter is detected before treatment, the apparatus comprising a light emitter for emission of a first light beam and deflection means for adjustable deflection of the light beam along a predetermined path and detector means for detecting at least one tissue parameter at the target area. The apparatus further comprises storage means for storage of coherent data sets of signal values provided by the detector means at positions along the predetermined path and the respective corresponding positions thereby mapping tissue parameters as a function of stored relative positions along the path and first light beam control means for controlling parameters of the first light beam along the predetermined path in accordance with the stored data sets.
According to a fourth aspect of the invention, a handpiece for an apparatus for cosmetic tissue treatment as described above is provided, comprising an input connector for connection of a first beam-outlet end of a first optical fiber to the handpiece and for alignment of the first optical fiber with an axis of the handpiece so that a first light beam emitted from the first beam-outlet end is transmitted substantially along the axis. The handpiece further comprises an output for emission of the deflected first light beam towards a target area of tissue to be treated and detector means for detecting the type of tissue at the target area. The handpiece still further comprises first light beam control means for controlling parameters of the first light beam emitted towards the target area in response to the detected type of tissue.
According to a fifth aspect of the invention, an apparatus for cosmetic tissue treatment is provided, comprising a light emitter for emission of a first light beam, means for directing the first light beam towards a target area to be treated, detector means for detecting at least one tissue parameter at the target area, the tissue parameter being selected from the group consisting of texture, elasticity, size, and shape, and first light beam control means for controlling at least one parameter of the first light beam in response to the detected at least one tissue parameter.
Certain types of tissue, such as small marks on the tissue such as marks from chloasma, liver spots, red spots, tattoos, blood vessels, beauty spots, freckles, etc, to be treated are characterized by the shape or the size of the area covered by the type of tissue in question. For example, when treating different types of marks of substantially identical colors it may be desirable to treat each type of mark differently and according to the respective size or shape of the type of mark in question.
When the apparatus is kept in a fixed position in relation to a target surface which is illuminated by the first light beam changing of the position of the deflection means causes the first light beam to traverse or scan the target surface along a path or a curve. An area may be traversed or scanned by the first light beam, e.g. by letting the first light beam traverse or scan a meander like path substantially covering the area or, by traversing or scanning the area line by line. In the present context, the type, number and shape of paths traversed by the first light beam in order to traverse a specific area is denoted the traversing pattern or the scan pattern. The area that is scanned or traversed by the first light beam is denoted the scan area, the treatment area or the traversed area. The first light beam may treat the surface at the target area and the first light beam may therefore be denoted the treating light beam.
Cellular water absorbs light energy, and applying light energy to the cells is therefore an efficient way of ablating tissue. Thus, it is preferred to use light sources, such as lasers, generating light at wavelengths with a high absorption in water, preferably wavelengths larger than 190 nm, such as wavelengths in the range from 190 nm to 1900 nm, preferably from 700 nm to 900 nm, and even more preferred approximately 810 nm, or, preferably wavelengths larger than 1900 nm, such as wavelengths in the range from 1900 nm to 3000 nm, preferably from 1900 nm to 2200 nm, preferably from 1900 nm to 2100 nm, or, from 2800 nm to 3000 nm, and even more preferred approximately 2930 nm, or wavelengths equal to or greater than 4500 nm, such as wavelengths in the range from 4500 nm to 11000 nm, preferably from 4500 nm to 5500 nm, alternatively from 10000 nm to 11000 nm, such as around 10600 nm.
The apparatus according to the invention may be used for ablating a thin epidermal layer of the derma of a patient, removing marks on the tissue, such as marks from chloasma, liver spots, red spots, tattoos, blood vessels just below the surface, etc, as well as warts, wounds, hair follicles, etc, and hereafter the terms tissue and resurfacing will include these marks and treatments thereof.
It is preferred, that the light source utilized in the present invention is a laser, but other light sources, such as light emitting diodes and halogen bulbs, may be utilized. The laser may be any laser capable of emitting light with sufficient power for illuminated cells to vaporize, such as CO2 lasers, YAG lasers, such as Erbium YAG lasers, Holmium YAG lasers, Nd YAG lasers, etc., semiconductor lasers, pulsed lasers, gas lasers, solid state lasers, Hg lasers, excimer lasers, etc.
Present CO2 lasers emit light at a wavelength of 10600 nm. The CO2 laser is particularly well suited as a light source in an apparatus for ablating dermal cells as water has a high energy absorbance at 10600 nm and the CO2 laser is capable of reliably delivering the required laser power.
Erbium YAG lasers emit light at a wavelength of 2930 nm. Water absorbs less energy at this wavelength that at 10600 nm. Therefore, the Erbium YAG laser may be preferred for ablating thinner layers of dermal cells than may be ablated with a CO2 laser. Tissue having been treated with light emitted from an Erbium YAG laser may heal faster than tissue having been treated with CO2 laser light as a thinner layer of dermal cells is influenced by Erbium YAG laser light. An Erbium YAG laser may also be preferred when photocoagulation of blood vessels should be avoided.
A CO laser emits light in the 4500 nm to 5500 nm wavelength range. Water absorption at these wavelengths is somewhat less than water absorption at 10600 nm. A CO laser light source is presently preferred for dental treatment, e.g. for removal of carries, as dentine is not influenced by illumination of light from a CO laser.
A Nd YAG laser with a frequency doubled output beam in the 520-680 nm wavelength range is presently preferred as a light source for treatment of hypervasculation. Light in this wavelength range causes photocoagulation of blood without affecting surrounding tissue provided that an appropriate intensity of the light beam is directed towards the micro vessels-for an appropriate period of time. Coagulation stops blood flow in the treated vessels whereby discoloration of the skin also stops.
Typically, a power density greater than about 50 W/mm2, such as a power density in the range from about 50 W/mm2 to about 180 W/mm2, is adequate for vaporizing cells with a minimum of damage to the surrounding tissue.
However, when removing hairs, the wavelength of the light is preferred to be approx. 800 nm. At this wavelength the absorption of the light in the hair follicles is lower than at higher wavelengths, and the power density must therefore be higher than 180 W/mm2, preferable higher than 300 W/mm2. Generally, the power density is adapted to the wavelength and the tissue to be treated.
The optical fiber for interconnection of a light source with a handpiece according to an embodiment of the present invention may be any fiber, such as a poly-crystalline silver halide fiber, etc, that is suitable for transmission of light emitted from the light source and that is made of a material that allows repeated bending of the fiber, so that an operator can freely manipulate the handpiece in order to direct the light beam towards various areas of a patient.
A handpiece is a single unit for conveniently holding in one hand by an operator of the handpiece.
It is preferred to shape the handpiece ergonomically so that a comfortable hand grip is provided for the operator of the apparatus. For example, it is preferred to direct the light beam towards a target area at a substantially right angle to the area. The ergonomic form of the handpiece allows the operator to point the light beam at a substantially right angle to the target surface without having to bend the wrist in an uncomfortable way.
Preferably, the handpiece is light so that it is easy for the operator to hold the handpiece and bring it into any desired position in relation target surface to be treated. The weight of a preferred handpiece according to the present inventionxe2x80x94cables and fibers not includedxe2x80x94is less than 500 grams, such as 290 grams, or such as 250 grams.
User interface means may be provided for selection of parameters relating to the operation of the apparatus. According to a preferred embodiment of the invention comprising a handpiece, the user interface means are positioned on the housing of the
The parameters may comprise traversing velocity of the output light beam from the handpiece, intensity of the output light beam emitted form the handpiece, size of the target surface area to be traversed by the output light beam, shape of the target surface area to be traversed by the output light beam, etc.
The user interface means may comprise a first button, e.g. a membrane switch, for selection of a parameter type by stepping through a set of parameter types, such as the set listed above or any subset thereof.
The user interface means may further comprise a second button, e.g. a membrane switch, for selection of a parameter value of the parameter type currently selected by stepping through a corresponding set of parameter values.
A set of light emitting diodes may be provided for indication of the set of currently selected parameter values.
It is an important advantage of provision of the user interface at the handpiece that an operator of the handpiece is able to simultaneously select operational parameters of the handpiece and observe resulting changes in treatment effects as the operator is not forced to shift his field of view from the surface area to be treated to a user interface panel positioned somewhere else, e.g. behind the operator.
Preferably, the buttons are positioned on the housing of the handpiece so that single-handed operation is possible, preferably, with the right as well as with the left hand.
The user interface means may further comprise a foot pedal. The first light beam traverses a target surface area when the operator depresses the pedal. Preferably, first light beam traversing is stopped immediately when the operator releases the pedal and the emission of the first light beam towards the target surface area is prevented.
As already mentioned, it is desirable to automatically control whether or not tissue towards which the first light beam is directed or towards which the handpiece is directed (the handpiece is said to be directed towards a specific area if that area is illuminated when the light beam emitted by the handpiece is turned on) is treated and to what extend it may be treated. For example, if the first light beam or the handpiece is directed towards healthy tissue, turn on of the first light beam may be inhibited or the laser parameters may be controlled so that no damage will be induced in the healthy tissue.
Tissue may be classified into specific tissue types according to predetermined values of various parameters, such as color, temperature, texture, elasticity, size, shape, etc.
For example, various marks may be detected by their color. Thus, the detector means may comprise light detectors for detection of intensity of light emitted from tissue at the target area, the target area being the area to be treated by the first light beam or being the area the handpiece is currently directed at.
The light detector is preferably a semiconductor light detector, such as a photodiode, etc.
The light detector means may be positioned inside the handpiece.
The target area may be illuminated by a light source, such as a white light source, and the reflected light from the target area may be detected by the detector means and analysed so as to characterise the type of tissue that is illuminated.
Further, light sources emitting light of different predetermined wavelengths may be directed towards the target area. For example, the light sources may comprise two light emitting diodes, one for emission of light in the wavelength range where the light is considered red and the other for emission of light in the wavelength range where the light is considered green. Also the light sources may comprise three, four or even more light emitting diodes for emission of light of different wavelength ranges. The light sources may alternatively emit light in the ultra violet or infrared wavelength range. Light from the light sources is transmitted towards the target area and is reflected by tissue at the target area. The reflected light is detected by the detector means and the intensity of reflected light in the two or more wavelength ranges in question characterizes one or more parameters of tissue that is illuminated.
The light source or light sources illuminating the target area may be positioned inside the handpiece.
The first light beam control means comprises outputs for controlling various parameters of the first light beam emitted by the light emitter, such as wavelength, output power, duty cycle, etc. Based on tissue parameter or tissue parameters as measured by the detector means, the first light beam control means adjusts parameters of the emitted light correspondingly. For example, when two light sources are utilized for detection of tissue parameters as previously described, predetermined reflected light intensity value ranges for the two wavelength ranges may be stored in a memory of the first light beam control means. During treatment, measured values of reflected light intensity are compared with the stored predetermined ranges and when measured values are within the stored ranges treatment is enabled and otherwise it is disabled.
Treatment may be disabled by stopping the emission of the first light beam by shutting off the light emitter or by inserting a shutter in the path of the first light beam. Alternatively, the parameters of the light emitter emitting the first light beam may be controlled so that tissue at the target area is not influenced by the first light beam.
Further, the wavelength and/or the power of the first light beam emitted by the light emitter may be adjusted according to the measured values. For example, a plurality of predetermined ranges of reflected light intensity may be stored in the memory and during treatment the measured values may be compared to the stored ranges and the value of the wavelength and/or the power of the first light beam may be set according to relations between measured values and stored ranges. Alternatively, the first light beam control means may calculate and control the wavelength and/or the power of the first light beam as a predetermined function of measured values of reflected light.
The output power of the first light beam may be adjusted by adjustment of the continuous output power of the light emitter, by adjustment of the duty cycle of the light emitter, etc.
The apparatus for tissue treatment may comprise an infrared detector, such as an infrared photo detector, for detection of intensity of infrared light emitted from tissue at the target surface, e.g. for determination of the temperature of the tissue. Like color, temperature may be utilized for characterization of tissue types. Further, tissue temperature may be utilized for monitoring of treatment progress and quality. The temperature of treated tissue increases during treatment and measurement of tissue temperature may be utilized for verification of the effect of the treatment. For example, when a specific tissue temperature is reached within a specific area, treatment of that tissue may be terminated, e.g. further treatment may be inhibited, as sufficient treatment has already been accomplished. Further, if a certain temperature has not been reached during treatment, output power of the light emitter may be increased to increase efficiency of the treatment.
The infrared detector may be positioned in the handpiece.
Furthermore, a cooling fluid, such as water, such as a gel, etc. may be applied to the surface to be treated during treatment. For example, the fluid may be applied between two plates of a material transparent to the light beams to be used during treatment. The fluid may be positioned in a substantially closed reservoir between the two plates or the reservoir maybe provided with an in-let and an out-let whereby the fluid may pass through the reservoir to ensure constant cooling during treatment.
Thus, the apparatus may comprise a cooling member that is adapted to be positioned at the target area for cooling of tissue at the target area and that is at least partly transparent to the first light beam. The cooling member may comprise a frame, an upper window positioned in the frame, and a. lower window positioned in the frame, the frame, the upper window, and the lower window defining a volume therebetween for receiving and holding a cooling liquid. Further, the cooling member may comprise an inlet for inputting cooling liquid to the volume and an outlet for outputting cooling liquid from the volume. The cooling member may be attached to the handpiece.
To obtain an optimum result of treatment, it is important to keep the light beam focused at the target area during treatment.
The apparatus may comprise means for automatically controlling the distance from the apparatus to the focus point in such a way that the light beam is automatically focused at the target area during treatment. For example, if the handpiece comprises the means for automatically controlling, the distance from the handpiece to the focus point is controlled.
Thus, the detector means may comprise a detector array and array optics for forming an image of the target area on the array. Further, the detector means may comprise image processing means for processing output signals from the defector array.
Preferably, the image processing means is adapted to calculate the size of a spot on the target area illuminated by the first light beam, or another light source of the apparatus, and imaged onto the detector array.
The apparatus may further comprise output optics for focusing the first light beam onto the surface of tissue to be treated and movably positioned at the output of the apparatus for adjustment of the distance between the apparatus and the focus point, and focus control means for adjusting the position of the output optics in response to the value of the calculated spot size.
For example, the handpiece may comprise the output optics for focusing the first light beam onto the surface of tissue to be treated whereby the distance between the handpiece and the focus point is adjusted by adjusting the position of the output optics in response to the value of the calculated spot size.
According to another embodiment of the invention, two crossing visible light beams are emitted from the handpiece, the cross point of the beams indicating the focus point of the first beam. The image processing means are adapted to detect the number of spots imaged onto the detector array, and the focus control means are adapted to adjust the position of the output optics in response to the number of spots and, preferably, the distance between them (if more than one).
The deflection means may comprise any optical component or components suitable for deflecting light of the wavelength in question, such as mirrors, prisms, diffractive optical elements, such as holograms, grids, gratings, etc, etc.
The means for directing may comprise any optical component or components suitable for directing light of the wavelength in question, such as reflective elements, such as mirrors, etc, refractive elements, such as prisms, lenses, etc, diffractive optical elements, such as holograms, grids, gratings, etc, etc.
Further, the handpiece may comprise the deflection means.
The deflection means are preferably adjustably mounted for displacement of the deflection means as a function of time, so that the first light beam may traverse a surface along a predetermined path, while the apparatus is kept in a fixed position. Preferably, the deflection means are rotatably mounted, and the actual deflection of the light beam is determined by the current angular position of the deflection means. This is a particular advantage when the handpiece comprises the deflection means as the handpiece then may be kept in a fixed position during traversing of the surface target area whereby traversing of the surface is not depending on operator skills. Moving means may be utilized to control positions of the deflection and focusing means, such as actuators, such as piezo electric crystals, the displacement of which is controlled by applying a specific electric voltage to their electrodes, electromotors generating linear or rotational displacements, galvanometers, magnetically activated or controlled actuators, pneumatic actuators, hydraulic actuators, etc.
The positions of the deflection means may be controlled by deflection control means adapted to control the deflection means to deflect the light beam in such a way that it traverses a target surface along a predetermined path.
According to an embodiment of the invention, an apparatus is provided, having two mirrors that are rotatably mounted in the path of the light beam in the apparatus. The rotational axis of the mirrors may be substantially perpendicular to each other in order to obtain two dimensional deflection of the light beam. Further, a handpiece may be provided having the two mirrors rotatably mounted in the path of the light beam in the handpiece.
Alternatively, the deflection means may comprise one mirror that is rotatable around two axes that may be substantially perpendicular to each other.
The mirrors may be connected to electromotors for angular positioning of the mirrors, e.g. each mirror may be directly connected to a corresponding shaft of a motor, whereby each motor is used for angular positioning of the corresponding mirror.
In order to minimize the size of the handpiece, it is preferred to mount the motors with their respective shafts in a common plane. For example, one motor may be a linear motor, such as a linear step motor, generating linear displacements. The shaft of this motor may be connected to the mirror at a first edge of the mirror, while a second and opposite edge of the mirror is rotatably connected to the handpiece. By pushing or pulling the first edge by the linear motor, the mirror is rotated about its rotational axis. The other motor, preferably a galvanometer, may be connected to the other mirror in the conventional way described above, whereby the two mirrors may be rotated around substantially perpendicular axes.
The deflection control means may be adapted to control the deflection means so that the predetermined path is a substantially straight line.
Preferably, the deflection control means are adapted to control the deflection means so that the light beam traverses a target surface area line by line.
It is an important advantage of the line by line traversing pattern that areas of any arbitrary shape, such as polygonal, such as rectangular, quadratic, triangular, etc, or circular, elliptic, etc, may be traversed line by line by appropriately controlling the starting point and stopping point of light emission along each line traversed.
Preferably, the first deflection control means are adapted to control the first deflection means so that the lines are traversed sequentially i.e. neighbouring lines are traversed successively. This minimizes the requirement for the operator to be able to keep the handpiece steady in a desired position because when lines are traversed successively, neighbouring lines are traversed within a very short time period so that involuntary hand movements of the operator does not lead to traversing overlap i.e. involuntary hand movements can not within the very short time period during which a single line is traversed move the handpiece back to the line previously traversed which would lead to uneven treatment of the target surface.
If an interlacing traversing pattern were utilized, i.e. every second line of the target surface area is traversed and after that the remaining lines in-between are traversed, there would be sufficient time between traversing of neighbouring lines to allow involuntary movements of the handpiece to a line previously traversed leading to repeated treatment of one area that may damage tissue at that area and leaving another area without treatment.
Thus, a method is provided of traversing a light beam across an area of a tissue, comprising the steps of emitting the light beam towards the tissue area, deflecting the light beam with deflection means so that the tissue is traversed by the light beam line by line sequentially, each line being traversed in the same direction.
The first deflection control means may be adapted to control the first deflection means so that the lines are traversed in the same direction whereby substantially the same amount of power per area is delivered uniformly across the target surface area leading to substantially the same temperature increase at any point of the target surface area after traversing.
When a target area is traversed line by line, it is preferred that movement of one mirror causes the light beam to traverse a line while movement of the other mirror moves the light beam to the next line. In the example above, the galvanometer preferably generates the line traversing as the galvanometer can move the mirror at a high speed, and the linear motor preferably generates the displacement of the light beam to the next line to be traversed.
As mentioned earlier, it is preferred to control the amount of energy delivered to cells to be ablated, as the amount of energy must be sufficient for the dermal cells to vaporize and, simultaneously, the amount of residual energy heating non-ablated cells must be so low that non-ablated cells will not be seriously damaged. Thus, when an area of tissue is traversed, e.g. line by line, it is preferred that neighbouring lines substantially abut each other. Clinical investigations have shown that, typically, an overlap of 0.1 to 0.2 mm is acceptable, and a distance between traversed lines of up to 0.1-0.2 mm is acceptable.
In order to control positioning of paths on the target area this accurately, it is preferred to position the deflection means extremely accurately e.g. in the handpiece. In the preferred embodiment of the invention, this is accomplished by utilisation of printed circuit technology providing high accuracy of hole positioning of 0.05 mm. The mirrors are rotated around shafts that are mounted in printed circuit boards providing the required positioning accuracy. Further, the motors rotating the mirrors are also mounted on the printed circuit boards providing electrical connections to the motors and the mechanical support and positioning needed.
When traversing a target surface area line by line, it is preferred to traverse each line in the same direction ensuring uniform heating of cells across the target surface area. Further, it is preferred to turn off the light beam, e.g. by switching off the light emitter, by inserting a light obstructing member in the light path of the beam, etc, while the light beam is moved from the end of a line having been traversed to the start of the next line to be traversed, in order to avoid repeated illumination of areas of the two lines.
Instead of turning the light emitter off, the light beam may be moved at a speed significantly larger than the traversing speed, during movement from the end of a line to the start of the next line.
Typically, the intensity within the beam of a light beam as generated by the light emitter varies as a normal function of the distance from the centre of the beam. The optical fiber may be designed or selected to be dispersive in such a way that the intensity function of the light beam emitted from the fiber as a function of the distance to the centre of the beam is substantially rectangular, i.e. the intensity of the beam leaving the fiber decays more slowly towards the edge of the beam than the intensity of a beam as generated by the light emitter whereby heat is more uniformly generated in cells across a traversed fine of tissue.
The detector means may be utilized for detection of various tissue parameters during scanning of the first light beam across a tissue area so that treatment and tissue parameter determination are performed substantially simultaneously including adjustment of light beam parameters according to detected tissue parameter values.
However, it is presently preferred that the light beam control means further comprises switching means for preventing emission of the first light beam and being controlled by the first light beam control means so that emission of the first light beam is prevented during a detecting scan from a predetermined first position to a predetermined second position along a predetermined path. During the detection scan the detector means detect light reflected from the target surface area along the predetermined path and the reflected light is analysed by the detector means or alternatively the reflected light is analysed by a microprocessor common to the controlling means analysing means of the apparatus.
The apparatus may further comprise tissue parameter storage means, such as an EEPROM, for storage of coherent data sets of signal values provided by the detector means at predetermined positions along the predetermined path of the light beam and the corresponding positions of the deflection means thereby mapping tissue parameters as a function of relative position within the target area of the tissue in the storage.
The storage means may comprise any memory, such as an electronic memory, such as an EEPROM.
The first light beam control means may further be adapted to control parameters of the first light beam during a second movement of the light beam along the above-mentioned predetermined path in accordance with the coherent data sets stored.
For example, without automatic control of tissue treatment, removal of hair is a difficult task to perform as a large number of small spots having diameters of approximately 1 mm have to be pinpointed by the operator performing the treatment. According to the present invention, the surface tissue area with hair to be removed is scanned by the apparatus, e.g. the handpiece. Hereby the hair follicles are detected by color determinations as described above and their positions along the scanned path of the light beam are stored in the tissue parameter storage means. During a second and repeated scan of the tissue area, the first light beam is turned on and off according to the content of the tissue parameter storage means so that solely the hair follicles detected during the first scan are treated preventing the surrounding tissue from being damaged. Alternatively, the parameters of the first light beam are regulated according to the content of the tissue parameter storage means so that in a first position the power-per-area of the light beam is adjusted so that the detected hair follicles are treated and in a second position the power-per-area of the light beam is reduced so that the surrounding healthy tissue is not damaged.
Parameter values, such as color, temperature, etc, stored in the tissue parameter storage may be displayed on a display unit, such as a CRT, LCD, etc, e.g. as graphical three dimensional plots showing surface profiles of the actual parameters of scanned areas. Further, the parameter values may be processed, e.g. providing averages, weighted averages, correlation, cross-correlation, etc, and the value may be displayed, e.g. on the display unit or, on a separate display on the handpiece.
By pulse width modulating the light emitter; energy delivered to the target surface may be varied along a traversed line in addition to the variations created by adjustment of parameters of the first light beam in response to detected tissue parameters. A fade-in area may be created by starting traversing of each traversed line with short pulses of light between longer periods of no light. As the line is traversed, the duration of the light pulses may be increased while the periods with no light may be decreased. Outside the fade-in area, the light beam may not be pulsed whereby the remaining part of each line is traversed with a constant intensity of the light beam.
Likewise, a fade-out area may be created by after having traversed a part of a line with constant light intensity, pulse width modulating the light source to transmit shorter and shorter pulses of light towards the line at the target surface area ending with no light transmitted at the end of the line.
The maximum amount of energy delivered by the first light beam to the target area is determined by the fade-in or fade-out function and can not be exceeded by the adjustment of parameters of the first light beam. However, the adjustment may result in a amount of energy delivered that is lower than the maximum amount of enegy.
The fade-in or fade-out traversing patterns may also be created by gradually increasing or decreasing, respectively, the power of the light source, or by decreasing or increasing, respectively, the traversing speed of the light beam.
Alternatively, a combination of these methods may be used.
The shape of the traversed area including the fading area may for example be polygonal, such as rectangular, quadratic, triangular, etc, circular, elliptic, etc.
A traversed line with fade-in and/or fade-out provides a smooth transition from a non-ablated area of tissue to an ablated area of tissue. This is a particularly advantageous feature when the apparatus according to the present invention is used for treatment of small marks on the tissue such as marks from chloasma, liver spots, red spots, tattoos, blood vessels etc.
Light intensity control means may be provided for generating a control signal for transmission to a light emitter interconnected with the optical fiber and controlling intensity of light emitted by the light emitter and transmitted through the optical fiber.
The fade-in and fade-out may be provided by controlling the intensity of the light beam and/or the velocity of the traversing light beam along a predetermined path and the light intensity control means andlor the deflection control means may be adapted to provide fade-in and fade-out.
The light intensity control means and/or the deflection control means may be adapted to control the intensity of the light beam and/or the velocity of the traversing light beam along a predetermined path as a function of the position of the light beam inside the area of the target surface area.
To provide the normal ablating of tissue, the light intensity control means may be adapted to provide a substantially constant intensity of the light beam and the deflection control means may be adapted to provide a substantially constant velocity of the traversing light beam when the traversing light beam is inside a first part of the target surface area.
If desired, the fade-in and fade-out effect may be provided either by scanning the light beam with a velocity larger than the substantially constant scan velocity within the treatment area of tissue or, by decreasing the output power of the first light beam.
The first light beam control means may be adapted to control the power-per-area of the light beam when scanned along a predetermined path on a target tissue area to be treated. For example, when ablating tissue it is presently preferred to maintain the power-per-area of the first light beam inside a first part of the target tissue area at a substantially constant level.
In order to create the fade-in or fade-out effect, the power-per-area of the light beam when outside a first part of the target tissue area may depend on the distance to the first part of the target tissue area, and it is preferred that the power-per-area of the light beam increases with decreasing distance to the first part of the target tissue area.
Keeping the intensity of the light beam substantially at the constant level as provided inside the first part of the target tissue, fade-in and fade-out may be provided by traversing the light beam with a velocity larger than the substantially constant traversing velocity within the first part of the target tissue area.
Likewise, keeping the velocity of the traversing light beam substantially constant inside the first part of the target tissue, the fade-in and fade-out may be provided by emitting a light beam with a smaller intensity than the substantially constant intensity of light emitted within the first part of the target tissue area.
The light intensity control means and/or the deflection control means may be adapted to provide a varying Intensity of the light beam outside the first part of the target surface area. The intensity of the light beam may be varied between a first intensity being substantially identical to the substantially constant intensity in the first part of the target tissue area and a second intensity being an intensity at substantially zero, i.e. no light is emitted from the output of the handpiece or the second intensity may be an intensity of which no damage is injured in the tissue.
The user interface means may also enable selection of parameters relating to fade-in and fade-out, such as traversing velocity of the output light beam from the apparatus, e.g. the handpiece, in the fade-in or the fade-out area, intensity of the output light beam emitted from the apparatus in the fade-in or the fade-out area; size of fade-in or fade-out areas, shape of fade-in or fade-out areas, etc.
In the case where the first light beam is invisible, e.g. utilizing an infra red emitter, an ultra violet emitter, etc, a light source generating visible light may be provided for generating a visible light beam that is used to assist the operator by indicating areas towards which the invisible and treating light is directed during traversing. For example, the input connector of the handpiece may be further adapted to connect a second beam-outlet end of a second optical fiber for transmission of a visible light beam to the handpiece. The second optical fiber is preferably properly aligned in the connector in relation to the predetermined path of the visible light. The handpiece may further comprise second deflection means for adjustable deflection of the visible light beam in such a way that the first light beam and the visible light beams emitted from the output of the handpiece illuminate substantially the same area of a target surface.
Further, two crossing visible light beams may be emitted from the apparatus or the handpiece, the cross point of the beams indicating the focus point of the first light beam.
Preferably, common deflection means are utilised for deflection of all light beams emitted from the apparatus or the handpiece whereby tracking of the light beams are easily accomplished. The deflection means may thus comprise Zinc selenite lenses, as they are transparent for visible light as well as for infra-red light.
In order to further assist the operator of the apparatus, the visible light beam may, e.g. between traversing with the first light beam, be traversed around at least a part of the circumference of the target surface area thereby indicating the size, shape and position of the target surface area to be traversed with the first light beam.
When a polygonal shape of the target surface area has been selected, the visible light beam may, e.g. between traversings by the first beam, be scanned along one edge of the polygon.
Thus, the method may further comprise the step of transmitting a visible light beam towards the target surface area utilizing the first deflection means.
The method may further comprise the step of traversing the visible light beam along at least a part of the circumference of the target surface area to be traversed by the first light beam.
In order to further assist the operator of the apparatus, the temperature of the target tissue area may be measured immediately after treatment. The surface temperature is measured by measuring the infrared irradiation from the surface with an infrared detector, which may be comprised in the detector means of the handpiece. This temperature provide an objective measure of the quality of the treatment. A high temperature in the surface skin indicates that the energy has been absorbed in the surface tissue, whereas a low surface temperature indicates that the energy has been absorbed in the depths of the tissue. It is also possible to provide an interface to a PC (or any other calculating unit) for further calculations on the temperature data.
In order to still further assist the operator of the apparatus in keeping a constant distance from the output of the handpiece to the surface of the tissue to be ablated, the handpiece may comprise a distance member connected to the handpiece at the output with fastening means.
As the distance member will touch the patient, it is desirable to insert a new, disinfected member before treatment of a new patient and thus, it is preferred that the fastening means comprises a magnet so that a used distance member can easily be disconnected from the handpiece, e.g. for autoclaving, and so that a new member can easily be connected to the handpiece.
In order to increase the ease of use of the apparatus, which may be on the form of a handpiece, it may be provided with interfacing means for selection of parameters of the cosmetic treatment apparatus. The interfacing means may comprise push buttons, selectors, rotary switches, etc. The interfacing means may also comprise a display for showing the mean temperature of the surface immediately after the treatment.
The parameters selectable from the apparatus may comprise the scan velocity, the ablating and the visible light beam intensities, the size and shape of the scan area, and fade-in and fade-out effects.
The apparatus according to the present invention may further comprise a processor for control of the apparatus and comprising one or more control means, such as deflection control means, light beam control means, light intensity control means, etc. The processor may further be connected to the user interface means and may be adapted to control the functions of the handpiece in accordance with the user interface selections.
Thus, the processor may be adapted to control energy density received by the target surface when traversed by the invisible treatment light beam.
Further, the processor may be adapted to control energy density received by the target surface at a specific position as a function of the position along a predetermined path traversed by the first light beam e.g. in order to provide fade-in and fade-out.
According to a preferred embodiment of the invention the processor means may be positioned inside the handpiece.
The processor may comprise a memory, such as an EEPROM, for storing of different parameters of traversing patterns and fade-in and fade-out patterns, such as target surface area size, traversing duration, etc. Further the processor means may comprise the storage means for storage of coherent data sets of signal values provided by the detector means at positions along the predetermined path and the respective corresponding positions thereby mapping tissue parameters as a function of stored relative positions along the path.
The apparatus, e.g. in the form of a handpiece may further be provided with a computer interface facilitating reception of traversing pattern parameters generated in a computer and transmitted to the apparatus for storage in the memory. The user interface may be utilized for selection of a specific traversing pattern from the set of patterns stored in the memory as previously described. The computer may be any programmable electronic device capable of storing, retrieving and processing data, such as a PC.
It is an important advantage of provision of a processor in the handpiece that signal lines between the handpiece and an external device controlling the handpiece are not needed. This reduces weight of the handpiece with cables connected. Further, electrical noise on control lines is minimized because of reduced lengths of the lines. Still further, control speed is increased as capacitance of a short line is small.
Various traversing patterns may be created on a PC and be downloaded to the memory of the handpiece. The patterns may be stored in the form of a table of parameters defining number of lines, length of lines, distance between lines, start and end points of fade-in and fade-out of each line, points of turn on and turn off of the traversing light beam, etc of each traversing pattern stored.
A traversing pattern box may be provided, containing a processor, a memory and interface means for storage of traversing patterns generated, e.g. on a PC and transmitted to the box through the interface means for storage in the memory. The interface means of the box and the computer interface of a handpiece may be interconnected and the various traversing patterns stored in the box may be transferred to the memory of the handpiece whereby traversing patterns created at a single PC may be distributed to a plurality of handpieces that may be situated remotely from the PC.